1. Field of the Invention
The present invention relates to a system for controlling a rotating mechanism of a robot, press or the like, and more particularly to a system for preventing a false drive signal which may be produced from a drive control circuit by a slight rotation of the input shaft of a rotary encoder for detecting the rotational angle of the rotating mechanism.
2. Description of the Prior Art
In a rotating mechanism of a robot, press or the like, there has been used a system for controlling the rotating mechanism. One known system includes a so-called electronic rotary cam including a rotary encoder or the like and adapted for electronically detecting the rotational angle of the rotating mechanism of the robot, press or the like and for producing an output signal. The output signal produced from the electronic rotary cam is entered in a control circuit which in turn produces a drive control signal for controlling the movement of the robot, press or the like.
Such a conventional rotating mechanism control system, however, has certain drawbacks and disadvantages. For example, when the electronic rotary cam is in process of stopping after rotation or when it is stopped, its angular position may be just on the border of the output signal of the electronic rotary cam, and in such a case, the input shaft of the rotary encoder is slightly rotated through, for example, backlash of the rotating mechanism. Then, the electronic rotary cam produces an output signal which causes the control circuit to produce a false drive control signal. Consequently, the robot, press or the like which is expected to stop receives an operation instruction which will cause troubles such as unintentional movement of a robot arm and abnormal operation of the press, resulting in an accident or production difficulty.